The present invention relates generally to friction clutches used in vehicles and, in particular, to clutch brakes utilized in non-synchronized heavy-duty transmissions. Such brakes are activated upon disengagement of a main clutch to retard the rotation of transmission gearing for easier gear shifting.
It is well known in the art to retard vehicle transmission gears prior to gear shifting by using a clutch brake activated by a throw-out mechanism upon disengagement of the main clutch. Torque limiting clutch brakes which provide a limited amount of braking torque are also well known, and are widely preferred because of their durability and long life.
Resilient means have been used in torque limiting clutch brakes to cushion the braking effect and to prevent excessive braking pressure which may damage the clutch brake. For example, prior art devices have included opposed Belleville springs for establishing a predetermined frictional load between the inner and outer members of clutch brakes. However, clutches utilizing opposed Belleville springs must be carefully and accurately designed and assembled to evenly balance one spring against the other. An imbalance between the springs can cause one to overcome the other, flipping or reversing its concavity, thereby reducing the effectiveness and shortening the life of the clutch brake. Furthermore, such springs tend to concentrate a load over a small surface area thereby tending to spread the covers apart and cause excessive wear on the exterior friction surfaces.
Prior art clutch brakes were often designed with cover assemblies which act as heat sinks for heat originating both externally and internally of the cover assembly. In such devices, excessive wear in the cover facings may result in excessive heat built up in the cover assembly which may cause premature deterioration of the friction facings.